SAI:Taker - Futari no Artemis

In a future where a vital energy known as "Life" is crucial, individuals called "Sai Takers" can use devices called "Sai" to harness it and gain abilities. A rarer subset, "Original Takers," can manipulate "Life" without devices and are immortal unless they deplete it. They remain hidden from public view. A teenage boy named Kyouya moves in with two girls, Kyouka and Yuma, after losing his parents. Yuma is a "Sai Taker," while Kyouka is an "Original Taker." During a visit to test a new device modeled after Kyouka's, a terrorist attack occurs, prompting her to bind Kyouya to the device to save his life. The device causes unexpected effects, including transforming him into a girl. Now an "Original Taker" and disguised as a girl, Kyouya enrolls in an elite "Sai Taker" school with Yuma. He must manage his "Life" to survive and deal with the unknown consequences of the device.